The present invention relates to an electronic cash register for determining whether a key-in operation by one of various function keys is a valid key-in operation or an invalid key-in operation in each of a number of modes, and for prohibiting processing based on the key-in operation of the function key when it is determined to be invalid.
A mode switch arranged in an electronic cash register generally selects the "OFF", "REG", "RF", "PR", "X" and "Z" positions corresponding to the following respective modes. The "OFF" position of the mode switch corresponds to the mode in which the electronic cash register is not used in practice. The "REG" position corresponds to the mode in which normal cash registration is performed. The "RF" position corresponds to the mode in which partial refund of the registered amount of money is performed. The "X" position corresponds to the mode in which storage data is read out without being lost. The "Z" position corresponds to the reset mode in which all the storage contents are cleared after data is read out. The "PR" position corresponds to the preset mode in which preset data is stored in the memory. The range of selection of the mode positions differs in accordance with the type of key inserted in the mode switch. Generally, the "OFF" and "REG" positions can be selected by a key which is usually used by the operator, and the "OFF", "REG", "RF", and "PR" positions can be selected by a key which is usually used by the manager. Furthermore, all the positions can be selected by a key which is usually used by the owner. The function keys such as the "Rc" (receipt), "Pd" (paid-out) and "Ns" (no sale) keys can be generally used by the operator. However, in order to control the cash register operation, it is desirable that the function keys be controlled by the key used only by the manager. Furthermore, there are cases in which use of the function keys of an electronic cash register may vary in various countries, and the user may wish to use a function key for a mode different from the original mode. In the above cases, since the mode switch irrevocably determines the functions, inconvenience results.